The present invention relates generally to crop harvesting machines, commonly referred to as windrowers and, more particularly, to a novel drive system for providing reciprocating motion to a twin sickle bar cutting means.
Generally, windrowers cut a wide swath of crop, consolidate it and pass it through a set of conditioning rolls whose length is less than the length of the cutting means. A single sickle bar element has traditionally been the source of the crop cutting capabilities, an example of which can be found in U.S. Pat. No. 3,324,638 granted to Koch et al, on June 13, 1967. However, with increasingly wider cutting widths, it has been found to be advantageous to utilize a twin sickle cutting means such as revealed in U.S. Pat. No. 3,577,716 granted to McCarty et al. on May 4, 1971. Among the different devices which constitute the various types of crop consolidating means are draper conveyors and augers, such as the consolidating auger found in U.S. Pat. No. 3,324,639 granted to Halls et al. on June 13, 1967.
Presently utilized twin sickle drive systems are normally incorporated in self-propelled crop harvesting machines whereby the source of power is from a centrally located power take-off (p.t.o.) on the base unit. The transfer of power to the opposite sides of the header is accomplished via a common shaft running transverse along the header above the discharge opening and driven by the centrally located power source as in U.S. Pat. No. 3,503,190 or via individual shafts interconnecting the respective drive unit located at the side of the header and the centrally located power source. Examples of this second method are revealed in U.S. Pat. No. 3,283,485 granted to Koch et al. on Nov. 8, 1966, U.S. Pat. No. 3,304,699 granted to Koch et al. on Feb. 21, 1967, U.S. Pat. No. 3,771,297 and the aforementioned U.S. Pat. No. 3,577,716.
A modern design of a pull-type windrower, commonly referred to as a pivot tongue windrower, can be viewed in U.S. Pat. No. 4,081,946 granted to Ehrhart on Apr. 4, 1978. Generally, the primary source of power is provided by a hydrostatic motor connected to a hydraulic system which incorporates the arched draft member as a fluid reservoir. Hydrostatic motors are particularly susceptible to torque peaks caused by variable power requirements within the header drive system. In the design and development of such a crop harvesting machine, it was found that a novel drive system was needed for transmitting reciprocating motion to the dual sickle bar elements. However, to reduce excessive vibrations, the reciprocating motions of the dual sickle bars must be properly timed with respect to each other.